Baseband processor and a method of transmitting commands to a radio-frequency subsystem and radio telecommunication apparatus incorporating the baseband processor

ABSTRACT

The baseband processor ( 18 ) comprises: a storage unit ( 72 ) storing: a descriptor table comprising for each descriptor: a pointer field designed to point to a definition of an operation, an absolute operation time field indicating at which time from the beginning of a frame processing the corresponding operation should be carried out, an operation definition table comprising for each operation a definition of the operation, each definition having a sequence of events, each event of the definition table being associated with a relative event time field indicating at which time from the beginning of the operation the corresponding event should be executed, and a calculator ( 70 ) to automatically compute a list of events from the description and operation tables.

FIELD OF THE INVENTION

The present invention relates to a baseband processor and a method oftransmitting commands to a radio-frequency subsystem, and a radiotelecommunication apparatus incorporating the baseband processor.

BACKGROUND OF THE INVENTION

More precisely, the invention relates to a baseband processorcomprising:

-   -   a memory to store a list of events wherein each event of said        list is associated with an absolute event time field indicating        at which time from the beginning of the frame processing the        event should be executed,    -   an interface with the radio-frequency subsystem, designed to        execute each event of said list of events in order to transmit        to the radio-frequency subsystem the corresponding command, each        event being executed during the frame processing at a time        corresponding to the value of the associated absolute event time        field, and    -   a calculator to compute and store said list of events in the        memory.

Baseband processors and radio-frequency subsystems are used, forexample, in GSM (Global System for Mobile communications), GPRS (GeneralPacket Radio Service) and EGPRS (Enhanced General Packet Radio Service)telecommunication apparatus such as cellular mobile phones to receive ortransmit radio signals which are organized into frames. The structure ofeach frame is normalized.

In conventional mobile phones, during reception of radio signals, theradio-frequency subsystem receives radio signals, converts the radiosignals into baseband signals and sends the baseband signals to thebaseband processor. Thereafter the baseband processor processes thereceived baseband signals and controls the man/machine interfaces of themobile phone according to the received basebands signals.

During transmission of radio signals, the baseband processor generates abaseband signal and sends it to the radio-frequency subsystem. Theradio-frequency subsystem receives the generated baseband signal andconverts it into a radio signal, which is sent over the air.

In order to correctly process a frame, the tuning or setting of theradio-frequency subsystem must be changed several times during theprocessing of one frame. For example, a frequency channel or a receivergain of the radio-frequency subsystem must be changed while one frame idbeing processed. To do so, the baseband processor transmits commands tothe radio-frequency subsystem at a predetermined time during the frameprocessing. Up to one hundred commands must be transmitted to theradio-frequency subsystem during the processing of one frame.

The time to send a command must be controlled with a time resolution assmall as a one quarter-bit period. For GSM apparatuses, a onequarter-bit period is, for example, equal to 923 ns.

In order to achieve such a fine time resolution, the calculator of thebaseband processor computes the list of events before the beginning ofthe frame processing.

During the frame processing, the interface executes this list of eventsso the behaviour of the interface is accurately controlled.

During each frame processing, it may be necessary to set theradio-frequency subsystem in a receiving mode, then in a transmittingmode and then back to the receiving mode. To set the radio-frequencysubsystem in the receiving mode, a sequence or a succession of commandsmust be transmitted by the interface to the radio-frequency subsystem.The sequence of commands corresponds to a sequence of events in the listof events. Hereinafter, such a sequence of events, which corresponds toa particular change in the setting of the radio-frequency subsystem iscalled an operation.

Therefore, if during the processing of one frame, the radio-frequencysubsystem must be switched to receiving mode two times, the list ofevents includes two times the same sequence of events.

To compute the list of events, a storage unit associated with thecalculator stores a predefined list of events. Before each frameprocessing, this predetermined list of events is processed in order tocancel any unnecessary events for the next frame processing.

Because oftentimes, during the processing of one frame the sameoperation must be repeated two or more times, the predetermined list ofevents must be repeated two or more times. This repetition of operationsresults in an ineffective use of the storage unit space.

SUMMARY OF THE INVENTION

It is accordingly an object of the invention to provide a bandbaseprocessor which requires smaller storage unit space.

With the following and other object in view there is provided inaccordance with the invention a baseband processor wherein the basebandprocessor further comprises:

-   -   a storage unit storing:        -   a descriptor table comprising for each descriptor:            -   a pointer field to point to a definition of an operation                to be carried out by said interface during the frame                processing,            -   an absolute operation time field indicating at which                time from the beginning of the frame processing the                corresponding operation should be carried out by said                interface,        -   an operation definition table comprising for each operation            a definition of the operation, each definition having a            sequence of events to be executed by the interface in order            to carry out said operation, each event of the definition            table being associated with a relative event time field            indicating at which time from the beginning of the operation            the corresponding event should be executed, and

wherein said calculator is designed to automatically compute said listof events from the description and operation tables.

With this baseband processor, if an operation A must be repeated twotimes during the processing of one frame, the storage unit onlycomprises a first and a second descriptor coding respectively for thefirst and second occurrences of operations A. The first and seconddescriptors comprise a pointer field pointing to the same definition ofoperation A in the operation definition table. Therefore, the sequenceof events corresponding to operation A is stored only once even if thisoperation has to be executed several times during the frame processing.As a result, a data structure made of the descriptor table and thedefinition table save storage unit space.

The features, so that:

-   -   the storage unit further comprises a data table having parameter        values,    -   at least one definition of the operation definition table has an        event associated with an unknown parameter value,    -   each descriptor which comprises a pointer field pointing to an        operation definition, definition of which comprises an event        associated with an unknown parameter value is associated with a        parameter value of the data table, and    -   the calculator replaces the unknown parameter value in a        definition with the parameter value associated with the        descriptor comprising a pointer field pointing to this        definition, in order to compute said list of events,        have the advantage to further save storage unit space since        operations which only differ by the value of one or more        parameters are recorded only once in the operation definition        table.

The features, so that:

-   -   the memory comprises a non-dedicated random access memory which        is connected to the calculator and to the interface through a        shared memory access bus,    -   the calculator stores the list of events in said memory using        the shared memory access bus, and    -   the interface reads the list of events in said memory using the        shared memory access bus,    -   the interface reads the list of events using direct memory        access technologies (DMA),        allow reallocation of the memory space of the random access        memory not used by the interface, to other applications carried        out by the calculator. Such a possibility does not exist when        the list of events is stored in a memory dedicated to the        interface of the baseband processor.

The features, so that the calculator comprises:

-   -   a main processor programmed to update the description table in        the storage unit in order to tune the radio-frequency subsystem        for the processing of the next frame, and    -   a coprocessor associated with the main processor, the        coprocessor being able to compute said list of events form the        stored tables in the storage unit,        have the advantage to reduce the work load of the main        processor. Indeed, the number of descriptors is far inferior to        the number of events in the events list. Therefore, since the        main processor processes less data, the work load of this        processor is decreased.

Other features of the claimed baseband processor are further recited inthe dependent claims.

The invention also relates to a method carried out by the above basebandprocessor and a storage unit used to realise the baseband processor.

The invention also relates to a radio telecommunication apparatusincorporating the claimed baseband processor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a radio telecommunication apparatusincorporating a baseband processor according to the invention,

FIG. 2 is a graph illustrating commands to process a GSM frame,

FIG. 3 is a schematic diagram of a data structure used in the basebandprocessor according to the invention, and

FIG. 4 is a flow chart of a method for transmitting commands to atunable radio-frequency subsystem according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a part of a radio telecommunication apparatus 6. By way ofillustration, this radio telecommunication apparatus is a GSM radiocellular mobile phone 6. Phone 6 is able to communicate with a basestation 4 of a radio cellular phone network using radio signals 8. To doso, phone 6 implements a TDMA (Time Division Multiple Access) technique.

Base station 4 is equipped with an emitter and a receiver to transmitand receive radio signals 8 from phone 6. Radio signals 8 are organizedin frames of 1250 bits of information. FIG. 2 illustrates such a frame10. Frame 10 comprises an RX slot, a “Mon” slot, and a TX slot. Duringthe RX and “Mon” slots, information is received by phone 6. During TXslot information is transmitted to base station 4 by phone 6. Moreprecisely, the RX slot represents the reception of a normal burst andthe “Mon” slot represents the power monitoring of an adjacent cell.

To receive or transmit such radio signals, phone 6 comprises aconventional tunable radio-frequency subsystem 16 and a basebandprocessor 18. Subsystem 16 is connected to an antenna 20 to receive ortransmit radio signals.

Subsystem 16 is able to convert a received radio signal into a basebandsignal and vice-versa. In other words, the main task of subsystem 16 isto remove a carrier from the radio signal or to add such a carrier to abaseband signal. Baseband signals are exchanged between processor 18 andsubsystem 16 through lines 22 . . . connecting subsystem 16 to processor18.

For setting or tuning subsystem 16, processor 18 is connected tosubsystem 16 through a three-wire bus 24, digital output lines 26 andone or more analog lines 28.

The three-wire bus 24 is used to transmit control messages called“telegrams”. For example, such telegraphs are used to change a frequencychannel of subsystem 16.

Lines 26 are two state lines which can be set either in a logic one orlogic zero state. For example, lines 26 are used to control an antennafront end switch in subsystem 16 to shift from a receiving mode to atransmitting mode and vice-versa.

Lines 28 are used to send analog signals. Such analog signals are, forexample, used to control a reference frequency of subsystem 16 and tocontrol a transmission power level.

Lines 30 to 32 of FIG. 2 represent the time variations of lines 26during the processing of frame 10.

A line 34 of FIG. 2 represents the time at which telegraphs are sent onbus 24 to process frame 10. Transmission of a telegraph is illustratedby a logic one state while an idle state is illustrated by a logic zerostate.

The sequence of commands sent between time t₀ and t₁ on FIG. 2 is usedto shift subsystem 16 in the receiving mode immediately before thebeginning of the RX slot of frame 10. The sequence of commandscorresponds to an operation A1.

Similarly, on FIG. 2, five other operations B1, C, D, A2 and B2 arerepresented, corresponding to sequences of commands sent between time t₂and t₃, t₄ and t₅, t₆ and t₇, t₈ and t₉, and t₁₀ and t₁₁, respectively.Here, operations B1 and B2 shift the subsystem out of the receivingmode. Operation C shifts subsystem 16 into the transmitting mode.Operation D shifts subsystem 16 out of the transmitting mode. OperationA2 shifts subsystem 16 once again into the receiving mode. Operations A2and B2 are similar or identical to operations A1 and B1, respectively.

To transmit each command at the right time to subsystem 16, theprocessor 18 comprises a hardwired radio-frequency control interface 40and a random access memory 42.

Memory 42 is designed to contain a list of events 44. In this list, eachevent is associated with an absolute event time field and an event typefield. The absolute event time field indicates at which time theassociated event is to be executed during a frame processing. The eventtype field indicates which one among bus 24, lines 26 and lines 28 isconcerned with the associated event. For example, list 44 is athree-column table where the first column contains the events to beexecuted, the second column contains the associated event time field,and the third column the event type field.

The time in the absolute event time field is counted from the beginningof the frame to be processed. For a GSM frame, this absolute event timefield contains an integer number ranging from one to five thousand. Thisinteger number corresponds to the quarter-bit period number of a GSMframe. Therefore, number 1 corresponds to the first quarter-bit periodof the GSM frame, whereas number 5000 corresponds to the lastquarter-bit period of the GSM frame.

Memory 42 is connected to interface 40 through a memory access bus 46.

The interface 40 is able to execute every event of list 44 at thecorresponding absolute event time. To do so, interface 40 comprises aGSM timer 50, which counts the number of quarter-bit periods elapsedsince the beginning of the GSM frame processing. This timer 50 isconnected at a first input of a comparator 52. A second input of thecomparator 52 is designed to receive the numbers stored in the absoluteevent time fields of list 44. To read data in memory 42, interface 40uses a conventional DMA (Direct Memory Access) technology. An output ofthe comparator 52 is connected to an enable input of three blocks 54, 56and 58.

Block 54 is designed to send a telegram on bus 24.

Block 56 is designed to change the state of lines 26.

Block 58 controls the analog lines 28.

Interface 40 also comprises a hardwired controller 60, which controlsblocks 52, 56 and 58 in accordance with the events of list 44.

To compute list 44 and store it in memory 42, processor 18 comprises acalculator 70 and a storage unit 72.

For faster performance, the calculator 70 comprises a main processor 74and a coprocessor 76. Main processor 74 is a conventional programmablemicro-controller. The coprocessor 76 can be, for example, a DSP (DigitalSignal Processor) chip.

Micro-controller 74 is programmed to execute the method described inFIG. 3. However, microcontroller 74 is typically, also programmed tocontrol every user interface of phone 6 such as a monitor, keyboard,speaker and other elements.

The coprocessor 76 is especially designed to process the baseband signalreceived or transmitted through line 22. In order to do so, it comprisesanalog-to-digital converters 78, which converts the analog basebandsignal received through line 22 into a digital signal, and vice-versa.

More specifically, the coprocessor 76 is also designed to build list 44and to store it in memory 42. To do so, the coprocessor 76 is connectedto the memory 42 through bus 46. Bus 46 to access memory 42 is a sharedresource between interface 40 and coprocessor 76. Since memory 42 can beaccessed by different electronic applications of phone 6 through acommon bus 46, such a memory 42 is an undedicated memory.

Storage unit 72 is a dual port random access memory (DPRAM) or allowingdata exchange between microcontroller 74 and coprocessor 76. The firstport of storage unit 72 is connected to microcontroller 74 and thesecond port of storage unit 72 is connected to coprocessor 76.

To save space in storage unit 72, a special data structure 78 is used.

Data structure 78 is illustrated in more detail on FIG. 3. It comprisesa descriptor table 80, an operation definition table 82 and a data table84.

Table 82 comprises one operation definition for each similar operation.Here, four definitions 86 to 89 are represented. Definitions 86 through89 correspond to the definitions of operations A1 and A2, B1 and B2, C,and D, respectively.

The definitions of each operation have a similar structure. Therefore,only the structure of definition 86 will be described.

As an example, in FIG. 3, definition 86 has a four-column tablestructure. The four-column table structure comprises one row per eventof the sequence of events forming operation A1 or A2.

The cells of the first column are event fields. Each event fieldcomprises an event to be executed by interface 40. The cells of thesecond column are event type fields comprising an identifier of one ofblocks 54, 56 and 58. This identifier determines which block amongblocks 52, 56 and 58 executes the event of the first column.

The cells of the third column are relative event time fields. Eachrelative event time field contains the time at which the associatedevent of the first column is to be executed. The relative event time iscounted from the beginning of the operation rather than from thebeginning of the frame. This relative event time is, for example,recorded as an integer number of quarter-bit-periods elapsed since thebeginning of the operation. So a value of “200” in the relative eventtime field of the third row indicates that the third event of definition86 is to be executed 200 quarter-bit periods after the beginning of theoperation.

The cells of the last column are parameter fields, which contain eithera numerical value or an unknown value indicated, for example, by symbol“*”.

Advantageously, table 82 is a pre-recorded table.

Descriptor table 80 contains at least one descriptor per operation to beexecuted during one frame processing. Here, table 80 comprises a numberof descriptors equal to the maximum number of operations to be executedduring one frame processing. This maximum number is, for example, equalto 16 in the case of GSM frames.

In FIG. 3, only the seven first descriptors 90 through 96 arerepresented. Descriptors 90 through 95 correspond to operations A1, A2,B1, B2, C and D respectively. Descriptor 96 is an unnecessary descriptorfor the processing of frame 10.

Each descriptor comprises at least three fields:

-   -   a pointer field 98 pointing to the first row of the        corresponding operation definition in table 82,    -   a consecutive event number field 99 indicating the number of the        row in the associated definition, and    -   an absolute operation time field 100 indicating at which time        within the frame the corresponding operation should be executed.        The absolute operation time is counted from the beginning of the        frame processing. This absolute operation time is, for example,        recorded as an integer number of quarter-bit periods elapsed        since the beginning of the frame processing.

As an example, the pointer field of descriptor 90 comprises the addressof the first row of definition 86, the consecutive event number field 99is equal to 4 and the absolute time field is equal to 0.

In FIG. 3, the arrows indicate the definition to which each descriptoris currently pointing.

Table 84 contains the parameter values that should be used instead ofthe symbol “*” which is present in the definition of an operation. Byway of illustration only, table 84 is a one-column table, whichcomprises one row for each descriptor of table 80. More precisely, thefirst row is associated with the first descriptor of table 80, thesecond row is associated with the second descriptor of table 18, and soon.

Finally, data structure 78 also comprises an enable table 100. Table 100only comprises, for example one row, which contains one cell 102 perdescriptor. The first cell is associated with the first descriptor, thesecond cell is associated with the second descriptor and so on. Eachcell contains a boolean value “True” or “False”.

When the value of one cell 102 is set to “true”, that means that theassociated descriptor is to be used to compute list 44.

On the other hand, if the value of one cell 102 is set to “False”, theassociated descriptor must not be used to compute list 44.

The way in which processor 18 works will now be explained with referenceto FIG. 4 in the particular case of the processing of frame 10.

At initialization, for example, during the manufacturing process ofphone 6, table 82 is recorded, in step 110, in storage unit 72. Thentable 82 remains constant and unamended during every frame processing.

Before starting to process frame 10, calculator 70 computes a new list44 in step 112.

At the beginning of step 112, microcontroller 74 updates, in a sub-step114, the values contained in tables 80, 84 and 100. The values to beupdated to process frame 10 are determined in a conventional way inaccordance with the structure of frame 10.

In particular, during an operation 116, microcontroller 74 sets to“True” the value of cells 102 associated with descriptors 90 to 95. Thecells 102 associated with a descriptor, like descriptor 96, which is notneeded for the processing of frame 10 are set to “False”.

Then, microcontroller 74 amends, if necessary, during an operation 118,the value stored in the absolute operation time field 100 of descriptors90 to 95. Here microcontroller 74 stores in the absolute operation timefields 100 of descriptors 90 through 95, the respective valuescorresponding to time t₀, t₈, t₂, t₁₀, t₄, t₆ (FIG. 3).

Micro-controller 74 also amends, if necessary, during an operation 120,the parameter values stored in table 84.

Once every value necessary to process frame 10 has been recorded intables 80, 84 and 100, microcontroller 74 activates coprocessor 76.

Once activated, coprocessor 76 computes, in sub-step 124, list 44 fromthe data recorded in data structure 78.

To do so, coprocessor 76 builds, during an operation 126, a sorted listof descriptors. This list comprises the descriptors of table 80 whichare associated with a cell 102 containing the “True” value. This list issorted according to the value of the absolute operation time field fromthe first operation to be executed to the last one.

Then, in the sorted list of descriptors, coprocessor 76 replaces, duringan operation 128, each descriptor with the corresponding definitionpointed to by the pointer field 98. During operation 128, coprocessor 76replaces the symbol “*” appearing on the first row of definition 86 withthe corresponding parameter value read from the first row of table 84.

During operation 128, coprocessor 76 also calculates the absolute eventtime of each event by adding the values stored in the absolute operationtime field 100 and in the relative event time field.

Therefore, at the end of operation 128, coprocessor 76 has built a listof events sorted by absolute event time.

During an operation 132, this list is then stored in memory 42, as newlist 44. To execute operation 132, coprocessor 76 uses bus 46. Step 112ends, and interface 40 starts to process frame 10 in step 140.

During an operation 142, in step 140, timer 50 counts the number ofquarter-bit periods elapsed since the beginning of the processing offrame 10. This number is transmitted to the first input of comparator52.

In parallel, during an operation 144, interface 40 reads the valuecontained in the absolute event time field associated with the firstevent of list 44.

Still in parallel, during an operation 146, controller 60 reads theidentifier contained in the event type field of the first event of list44 and selects which block from blocks 54, 56, 58 will be used toexecute the corresponding event.

During an operation 148, comparator 52 compares the values on its firstand second inputs. When these values match, during an operation 150, theblock selected by controller 60 executes the corresponding event andthen returns to operations 144 and 146 in order to read and execute thenext event in list 44.

In operation 150, the selected block transmits to subsystem 16 a commandcorresponding to the executed event.

On reception of the transmitted command, the setting of subsystem 16 ischanged.

Steps 112 and 140 are executed for the processing of each frame.

Due to the use of data structure 78, the definition of an operation isstored only once, even if this definition is used at different timesduring the processing of one frame.

Further, due to the use of data structure 78, only one definition isstored for operations, which differ by a single parameter value.

Therefore, data structure 78 saves storage unit space.

Data structure 78 also decreases the work load of the microcontroller74. In fact, if the new list 44 to build differs from the previous one,only by the fact that one operation is delayed, microprocessor 74 hasonly to modify the absolute time field of the corresponding descriptor.In contrast, in conventional processors, to perform such a task, themicroprocessor has to update the event time field of each event of thesequence of events corresponding to this operation.

Processor 18 has been described in the particular case where memory 42is a non-dedicated random access memory. Since memory 42 is anon-dedicated memory, it means that the memory space non-utilized tostore list 44 can be used for other applications executed by calculator70. This also saves memory space since free memory space in memory 42can be used for other processes of applications.

In another embodiment, memory 42 is replaced by a bank of registerswherein each register is intended to receive only one event and itsassociated event time and event type fields. In such an embodiment, thebank of registers is connected to interface 40 by a reading bus and tothe calculator 70 by an independent writing bus. Thus registers, whichare not used to store list 44, cannot be used for other applications bycalculator 70.

In the present embodiment, memory 42 and storage unit 72 have beendescribed as independent and separate memories. However, in anotherembodiment, memory 42 and storage unit 72 can be different parts of acommon information storage means.

Phone 6 has been described in the particular case where subsystem 16 iscontrolled through the use of bus 24 and lines 26 and 28. However,depending on the radio-frequency subsystem implemented in telephone 6,one of these buses or lines may not be used and can be suppressed. Forexample, if the radio-frequency subsystem implemented in telephone 6only needs to be controlled through a three-wire bus, the architectureof telephone 6 is simplified. Indeed, lines 26 and 28 are suppressed aswell as blocks 56, 58, and controller 60 and the event type fields oftable 82 are no longer necessary.

Using coprocessor 76 to compute list 44 increases the speed ofprocessing because such a coprocessor is optimized for this processing.However, in another embodiment, the whole step 112 is carried out by themicro-controller 74. On the other hand, to further increase speedprocessing, in another embodiment, the whole step 112 is implemented ina specific hardwired circuit.

Processor 18 and phone 6 have been described in the special case of GSMframe processing. However, the invention also applies to GPRS or EGPRSframes or any radiophones where it is necessary to tune aradio-frequency subsystem with a very fine time resolution.

1. Radio telecommunication apparatus incorporating a baseband processorfor transmitting commands to a tunable radio-frequency subsystem theradio-frequency subsystem being designed to convert radio signals intobaseband signals and vice-versa, for tuning the radio-frequencysubsystem in synchronism with the processing of one signal frame, thisbaseband processor comprising: a memory to store a list of eventswherein each event of said list is associated with an absolute eventtime field indicating at which time from the beginning of the frameprocessing the event should be executed, an interface with theradio-frequency subsystem, designed to execute each event of said listof events in order to transmit to the radio-frequency subsystem thecorresponding command, each event being executed during the frameprocessing at a time corresponding to the value of the associatedabsolute event time field, and a calculator to compute and store saidlist of events in the memory, wherein the baseband processor furthercomprises: a storage unit storing: a descriptor table comprising foreach descriptor: a pointer field to point to a definition of anoperation to be carried out by said interface during the frameprocessing, an absolute operation time field indicating at which timefrom the beginning of the frame processing the corresponding operationshould be carried out by said interface, an operation definition tablecomprising for each operation a definition of the operation, eachdefinition having a sequence of events to be executed by the interfacein order to carry out said operation, each event of the definition tablebeing associated with a relative event time field indicating at whichtime from the beginning of the operation the corresponding event shouldbe executed, and wherein said calculator is designed to automaticallycompute said list of events from the description and operation tables.2. Radio telecommunication apparatus incorporating baseband processoraccording to claim 1, wherein: the storage unit further comprises a datatable having parameter values, at least one definition of the operationdefinition table has an event associated with an unknown parametervalue, each descriptor which comprises a pointer field pointing to anoperation definition, definition of which comprises an event associatedwith an unknown parameter value is associated with a parameter value ofthe data table, and the calculator replaces the unknown parameter valuein a definition with the parameter value associated with the descriptorcomprising a pointer field pointing to this definition, in order tocompute said list of events.
 3. Radio telecommunication apparatusaccording to claim 1, wherein: the memory comprises a non-dedicatedrandom access memory which is connected to the calculator and to theinterface through a shared memory access bus, the calculator stores thelist of events in said memory using the shared memory access bus, andthe interface reads the list of events in said memory using the sharedmemory access bus.
 4. The baseband processor according to claim 2,wherein the interface reads the list of events using direct memoryaccess technologies.
 5. The baseband processor according to claim 1,wherein the calculator comprises: a main processor programmed to updatethe description table in the storage unit in order to tune theradio-frequency subsystem for the processing of the next frame, and acoprocessor with the main processor, the coprocessor being able tocompute said list of events form the stored tables in the storage unit.6. A baseband processor for transmitting commands to a tunableradio-frequency subsystem, the radio-frequency subsystem being designedto convert radio signals into baseband signals and vice-versa, in orderfor tuning the radio-frequency subsystem in synchronism with theprocessing of one signal frame, this baseband processor comprising: amemory to store a list of events wherein each event of said list isassociated with an absolute event time field indicating at which timefrom the beginning of the frame processing the event should be executed,an interface with the radio-frequency subsystem, designed to executeeach event of said list of events in order to transmit to theradio-frequency subsystem the corresponding command, each event beingexecuted during the frame processing at a time corresponding to thevalue of the associated absolute event time field, and a calculator tocompute and store said list of events in the memory, wherein thebaseband processor further comprises: a storage unit storing: adescriptor table comprising for each descriptor: a pointer field topoint to a definition of an operation to be carried out by saidinterface during the frame processing, an absolute operation time fieldindicating at which time from the beginning of the frame processing thecorresponding operation should be carried out by said interface, anoperation definition table comprising for each operation a definition ofthe operation, each definition having a sequence of events to beexecuted by the interface in order to carry out said operation, eachevent of the definition table being associated with a relative eventtime field indicating at which time from the beginning of the operationthe corresponding event should be executed, and wherein said calculatoris designed to automatically compute said list of events from thedescription and operation tables.
 7. A method for transmitting commandsto a tunable radio-frequency subsystem, the radio-frequency subsystembeing designed to convert radio signals into baseband signals andvice-versa, in order to tune the radio-frequency subsystem insynchronism with the processing of a signal frame, the method comprisingthe steps of: recording in a memory a list of events wherein each eventof said list is associated with an absolute event time field, theabsolute event time field indicating at which time from the beginning ofthe frame processing the event should be executed, executing each eventof said list of events in order to transmit corresponding commands tothe radio-frequency subsystem, each event being executed, during theframe processing, at a time corresponding to the value of the associatedabsolute event time field, computing and storing said list of events inthe memory, and wherein the method further comprises: recording in astorage unit a descriptor table comprising for each descriptor: apointer field designed to point to a definition of an operation to becarried out by said interface during the frame processing, an absoluteoperation time field indicating at which time from the beginning of theframe processing the corresponding operation should be carried out bysaid interface, an operation definition table comprising for eachoperation a definition of the operation, each definition having asequence of events to be executed by the interface in order to carry outsaid operation, each event of the definition table being associated witha relative event time field indicating at which time from the beginningof the operation the corresponding event should be executed, andautomatically computing said list of events from the descriptor andoperation tables.
 8. A storage unit intended to be used in a basebandprocessor according to claim 6, wherein the storage unit comprises: adescriptor table comprising for each descriptor: a pointer field topoint to a definition of an operation to be carried out by saidinterface during the frame processing, an absolute operation time fieldindicating at which time from the beginning of the frame processing thecorresponding operation should be carried out by said interface, anoperation definition table comprising for each operation a definition ofthe operation, each definition having a sequence of events to beexecuted by the interface in order to carry out said operation, eachevent of the definition table being associated with a relative eventtime field indicating at which time from the beginning of the operationthe corresponding event should be executed.